“Direct-coated” sponge abrasives are materials in which abrasive mineral is coated on the surface of a resilient, cellular (sponge) material, such as foamed plastic, together with the relevant adhesives and binders. Although one or more resin layers may be coated on the foam prior to coating the abrasive, it is the foam itself which provides the overall structural integrity of the finished article, and largely determines its bulk physical properties such as tensile strength.
“Laminated sponge” abrasives are materials in which a conventional substrate, such as paper, cloth, etc. is coated on one side with abrasive grains and laminated by the other side to a sponge backing. Such laminated sponge abrasive materials are disclosed in DE 39 03 204; U.S. Pat. No. 4,263,755; and EP 0 578 865; and exemplified by the product sold under the tradename “SIASOFT” by SIA. Although the presence of the sponge layer confers useful properties such as resilience and insulation, the overall properties are determined to a significant extent by the substrate on which the abrasive is actually coated.
Direct-coated sponge abrasives show several advantages over their laminated sponge counterparts, including reduced raw material costs and an improved performance in terms of the smoothness of finish for a given rate of cut. Direct-coating of abrasive on to sponge materials is disclosed in various patents, e.g. U.S. Pat. Nos. 4,966,609; 4,629,473; 4,038,047; and 3,607,159; and UK Patent Nos. 1 597 455 and 1 472 087. Commercially available direct-coated sponge abrasive products are sold by 3M Company under the product numbers 03808, 03809 and 03810.
Such direct-coated sponge abrasives are generally intended for hand sanding where they are grasped by the user and rubbed against the workpiece with a suitable application of pressure. Thus, the user's hand and arm must supply a gripping action, a pressing action and a push-pull action, with the gripping action in particular potentially imposing strain and fatigue on the muscles and joints of the fingers when sanding is carried out over extended periods of time.
A variety of materials have been laminated to the reverse (non-abrasive coated) side of direct-coated sponge abrasive articles.
U.S. Pat. No. 4,966,609 discloses the use of a textile reinforcement (which may be any knit, woven or non-woven fabric) to provide increased strength and restrict extensibility. U.S. Pat. Nos. 4,629,473; 4,038,047; and 3,607,159 all disclose direct-coated sponge abrasive laminated to a backing member. The backing members include cloth, paper, plastic film, etc., and the backing member apparently contributes most of the mechanical strength of the finished article. UK Patent No. 1 472 087 discloses a foam pad having a coating of abrasive on one side and a coating of adhesive on the reverse. The adhesive enables the pad to be fixed to a suitable surface so that surgical tools or other implements may be cleaned by rubbing against the abrasive coating.
Hook and loop attachment systems are known and have been used for the attachment of abrasive articles to back-up pads, including the attachment of laminated sponge abrasive articles, as disclosed in EP 0 578 865 and DE 39 03 204. Hook and loop systems have also been used for the attachment on non-abrasive-coated foam buffing pads, as disclosed in U.S. Pat. Nos. 5,123,139 and 4,962,562.
U.S. Pat. No. 4,263,755 discloses a laminated sponge abrasive article in which the sponge layer itself functions as part of a hook and loop attachment system. This places severe restrictions on the type of sponge material that can be used, as only very open-textured materials give adequate engagement with the hooks or other protuberances on the back-up pad. Such materials do not function well as the self-supporting backing for a coated abrasive layer.
Various patents, e.g., UK 2 113 977; WO 87/04061; and WO 86/01090, disclose articles in the form of a glove having abrasive and/or cleaning elements releasably attached thereto. The hook and loop attachment system sold under the trade designation “VELCRO” attachment system is suggested as a possible attachment means, and the cleaning/abrading elements may comprise cellular materials.
It is known to use a strap or similar device to secure a sanding pad or block to a user's hand, the pad or block being releasably attached to an abrasive sheet, e.g., U.S. Pat. Nos. 5,222,331 and 4,202,139 and the hand sanding pad sold under the trade designation “EASYGRIP” hand sanding pad supplied by NicSand Inc. of Cleveland, Ohio.
The present invention provides direct-coated sponge abrasive materials adapted for being releasably secured to a hand strap, back-up pad, etc.